Human white adipose tissue (WAT) contains multipotent mesodermal progenitors, as deduced by several investigators who assayed the differentiation potential of the whole tissue, and, therefore, appears as an attractive, convenient, cheap and abundant source of therapeutic stem cells. In the present pilot study, we embark on the direct identification of these fat tissue-resident stem cells. Our general strategy is directly inspired by recent observations that include our own, showing that vascular endothelial cells and related mural cells, or pericytes, can be the source of early progenitors in the hematopoietic system, skeletal muscle and pancreas. The hypothesis we test in the present project is that this also applies to adipose tissue. To this end, endothelial cells and pericytes will be sorted to homogeneity, by flow cytometry, from the human WAT vascular stroma and introduced into assay systems, in culture and in immunodeficient mice, in order to document their ability to give rise to adipocytes, myofibers and hematopoietic cells. Understanding the differentiation potential of individual cell subsets sorted from a simple tissue such as WAT will be a step toward the identification of the elusive multipotent stem cells - mesenchymal stem cells (MSC), multipotent adult progenitor cells (MAPC) or muscle-derived stem cells (MDSC) - shown in the past few years to reside in adult organs. Fat tissue contains elusive stem cells that, if better characterized, could be used to repair diseased organs, for instance the muscle, bones and even the heart. Fat aspiration, which is commonly performed in cosmetic surgery, is a safe and easy procedure that could provide sufficient amounts of such therapeutic stem cells. These should be purified, in some instances stimulated in culture, then transplanted into the tissue to be repaired. We are in the process of identifying the localization and molecular characteristics of multipotent stem cells within human fat tissue. This project will further document the properties of these cells and lead to define methods for their prospective purification and development into diverse human functional tissues. [unreadable] [unreadable] [unreadable]